A fuel cell is an energy conversion device directly converting chemical energy of fuel into electric energy. In other words, a fuel cell employs a power generation method utilizing a fuel gas and an oxidizer, and using electrons generated during the oxidation and reduction reactions thereof to produce power. A membrane-electrode assembly (MEA) of a fuel cell is a part where an electrochemical reaction of hydrogen and oxygen occurs, and is formed with a cathode, an anode and an electrolyte membrane, that is, an ion exchange electrolyte membrane.
A redox flow battery (oxidation-reduction flow battery) is a system charged and discharged by active materials comprised of an electrolytic solution being oxidized and reduced, and is an electrochemical storage device directly storing chemical energy of the active materials as electric energy. A unit cell of the redox flow battery comprises an electrode, an electrolytic solution comprising an electrode active material, and an ion-exchange electrolyte membrane.
Due to their high energy efficiency and environmental friendly properties of low contaminant emissions, fuel cells and redox flow batteries have been researched and developed as a next generation energy source.
A core constituent in a fuel cell and a redox flow battery is a polymer electrolyte membrane capable of cation exchange, and properties of 1) excellent proton conductivity, 2) preventing electrolyte crossover, 3) high chemical resistance, 4) strengthening mechanical properties and/or 4) low swelling ratio are favorably required.